The present invention relates generally to storage batteries including aqueous electrolyte. It relates in particular to a battery wherein working masses are lead and manganese dioxide and the electrolyte is an aqueous solution including sulfuric acid, and wherein electrode-plates are formed from graphite.
A significant obstacle to the introduction of electric powered vehicles is the availability of suitable batteries at an acceptable cost. At present, conventional lead-acid batteries are most extensively used in electric powered vehicles. While other battery types such as nickel-zinc (Ni/Zn), nickel-iron (Ni/Fe), sodium-sulfur, (Na/S), aluminum-air (Al/Air), zinc-bromine Zn/Br, and lithium-iron sulfide (LiAl--FeS), are under development as a lighter, more efficient alternative to the lead-acid battery, they are still not widely accepted. This is due to a combination of factors including cost of materials, and complexity and cost of construction.
Desirable characteristics of a battery for electric vehicles include lightness, rapid charging rate, performance at low charge, ability to be charged and discharged many times without deterioration, and calendar lifetime. In addition, of course, the battery must have a high storage capacity per unit weight and should be capable of delivering high power over short periods to provide acceptable acceleration.
In a French Patent No 1,033,650 (Billioque), a battery is described which employs an electrolyte of copper sulphate and lead electrode-plates. The battery is constructed from an electrical series of physically isolated cells, wherein adjacent cells are physically isolated from each other by one of the electrode-plates. This electrode plate serves as a negative electrode for one of the adjacent cells, and as a positive electrode for the other. When the battery is charged, a layer of copper is deposited on one lead electrode-plate which is acting as a cathode, and oxygen is released from the electrolyte. The oxygen reacts with an adjacent lead electrode-plate, which is acting as an anode, to form a layer of lead oxide thereon.
It is taught in Billioque that an advantage of this cell construction is a relatively high charging rate compared with conventional lead-acid batteries. It is taught that it can be completely charged in less than one-quarter hour, while a conventional lead-acid battery requires several hours to completely charge. It is also taught that the battery can fully discharged in less that one-quarter hour, and that it is lighter in weight than a comparable lead-acid battery.
Despite the above described advantages, however, the battery of Billioque still requires lead electrode-plates which add significantly to the weight of the battery. Any electrode plate serving as an anode is corroded by the electrolyte. It is corrosion of electrode-plates by the electrolyte which is a significant factor leading to a limitation of the number of available charging cycles and of calendar lifetime in a conventional lead-acid battery, and presumably also in the battery of Billioque.